Proturans: Protura

Proturans have three distinct body regions (head; thorax, or midsection; and abdomen), no wings, and six legs, but they are not considered true insects. They form a group closely related to insects that includes springtails (order Collembola) and diplurans (order Diplura). All of these animals have mouthparts located inside a special pocket in their heads.

Proturans are small, pale, secretive animals ranging in size from 0.024 to 0.06 inches (0.6 to 1.5 millimeters). The head is cone-shaped and lacks eyes or antennae (an-TEH-nee). The needlelike jaws are directed straight ahead, with only their tips visible outside the head. On the top of the head is a pair of slightly raised, ringlike structures that help proturans smell their surroundings by detecting the presence of chemical compounds.

The front legs are long and bristling with sensitive, hairlike structures. These are the proturans' most important sensory structures, and they are usually curled and held high above the body like antennae. All of the legs have five segments and are tipped with a single claw. The species that live on the soil surface have longer claws than the species that burrow through the soil. Adult proturans have an eleven-segmented abdomen tipped with a distinctive taillike structure. The first three abdominal segments each have a pair of segmented appendages (uh-PEN-dih-jehz), or limblike structures, underneath. Most species breathe directly through the exoskeleton, or outer skeleton, but a few proturans have respiratory system made up of an internal network of breathing tubes.